Sunshine has emerged across far northern Illinois, but thunderstorms packing gusty winds and downpours have developed across central and southern portions of the state, generally along and south of I-80. The latest mesoscale discussion just issued by the Storm Prediction Center in Norman, Oklahoma acknowledges the potential for some strong/ severe thunderstorm development, but does not anticipate the issuance of a severe thunderstorm watch.
Mesoscale Discussion 1055 NWS Storm Prediction Center Norman OK 0440 PM CDT Sat Jul 14 2018 Areas affected...portions of southern into central IL Concerning...Severe potential...Watch unlikely Valid 142140Z - 142315Z Probability of Watch Issuance...20 percent SUMMARY...A few strong, locally damaging wind gusts will be possible late this afternoon across portions of central IL. A watch is not expected. DISCUSSION...Clusters of thunderstorms have become loosely organized across west-central IL this afternoon. A few severe gusts have been noted near the St. Louis metro area over the last hour and some linear organization has developed further north into central IL. Strong heating of a very moist boundary layer has resulted in MLCAPE greater than 2000 J/kg across the MCD area. Modest deep layer effective shear around 30 kt is present and likely aiding in the loosely organized cluster/line segment. Furthermore, steep low level lapse rates and PW values approaching 2 inches could result in a wet microburst or two. Eastward extent of the severe threat will be limited by earlier cluster of storms across east-central into southeast IL, which has stabilized the boundary layer. Given the limited area and isolated nature of the threat, a watch is not expected, but a few strong/locally damaging wind gusts will be possible.